He was sentenced to 180 days in jail, three years’ probation and mandatory sex offender registration.

Premarathne boarded a bus in Costa Mesa last October and sat next to a 16-year-old girl after talking to her at a bus stop, authorities said. During the bus ride, Premarathne began groping her thigh and crotch and tried to unzip her jeans.

During the assault, which lasted about 10 minutes, the girl began crying and ask him to stop, prosecutors said. Only when his cellphone rang did Premaranthe stop what he was doing.

The girl, whose name was not released, was able to get away and exit at her bus stop, authorities said. Her boyfriend's father picked her up shortly afterward and called police.

Prosecutors said Orange County Transport Authority records show Premarathne bought a bus pass and boarded buses 10 times that day.

A witness told police Premarathne was a Los Angeles transient who recently went to Orange County in search of work and frequently used bus transportation, officials said.

After further investigation by the Orange County Sheriff’s Department, Premarathne was identified on bus surveillance tapes and arrested Oct. 28 in Costa Mesa, the district attorney's office said.

Three teenage girls -- one from Orange County, one from Los Angeles and one from Long Beach -- claim to have been victims of Premarathne. One potential victim caught on a bus surveillance camera in Los Angeles County has yet to come forward, prosecutors said.

Anyone who believes they have been victimized by Premarathne or has additional information about him is asked to call supervising district attorney investigator Randy Litwin at (714) 347-8794.